This invention relates to filter elements and particularly to filter elements of the substantially tubular or candle type adapted to be supported at one end thereof by a tube plate, the tube plate being provided with a series of apertures for mounting a plurality of the filter elements.
The present invention stems from work to reduce the cost of filter maintenance in a situation in which downtime during filter repair or replacement is to be minimised and to facilitate access to filters. That situation arises for example in a large filter unit provided for large-scale industrial filtration.
In an existing unit in which the individual filter elements are each threadedly connected to the tube plate and are braced by interconnecting struts, it is necessary to cut away several elements to gain access to an element that has developed a fault before replacing the faulty element and the ones that have been cut away to gain access.
According to the invention a filter assembly comprises a tube plate supporting the open ends of a plurality of substantially tubular filter elements, the filter elements being provided in groups, the elements of each group being connected one to another in the group, and the arrangement being such that any group of elements can be detached from the tube plate and replaced by the same or a replacement group without detaching or cutting away the other groups of elements from the tube plate.
Although the elements are connected together in groups this need not affect the substantially uniform distribution of the elements across the area of the tube plate.
The connections between elements of a group are preferably provided at an intermediate position in the length of the filter elements, and preferably at substantially the midpoint in the length of the filter elements.
Each filter element preferably comprises a tube plate connector adapted to extend through a respective aperture in the tube plate, a blind end piece closing the e n d of the filter element remote from the tube plate connector, an intermediate tubular connector, and two cylindrical filter screens, a first of the filter screens extending between the tube plate connector and the intermediate connector, and the second filter screen extending between the tube plate connector and the blind end piece.
The tube plate connector preferably comprises a tubular spigot portion adapted to be received in a tube plate aperture, and an externally-threaded tubular portion axially adjacent to the spigot portion on the side towards the free end of the spigot portion.
Such a tube plate connector can be used to secure th e filter element to the tube plate by inserting the free end of the tube plate connector into the tube plate aperture, without any need for substantial turning of the filter element, applying a locking ring or nut to the free end of the tube plate connector, and by tightening of the locking ring, one or more suitable annular seals being provided between the tube plate connector and the tube plate, the arrangement being such that on tightening of the locking ring the element is secured firmly to the tube plate and a seal is effected between the tube plate and the exterior of the tubular spigot portion.
Preferably two substantially flat annular seals a reprovided, effecting a double seal arrangement, the arrangement comprising a single flat seal being provided between the locking ring and the tube plate, and a single flat seal being provided between the tube plate and the tubular spigot.
When each filter element comprises an intermediate tubular connector, the connections between elements of a group are preferably in the form of bridging elements extending between the intermediate tubular connectors.
The bridging elements are preferably welded to the intermediate tubular connectors and are preferably received at their opposed ends in external annular recesses provided in the intermediate tubular connectors.
The blind end piece of each element is preferably provided with an axially projecting pin adapted to be received in a respective aperture in a locating spider which helps to locate the closed ends of the filter elements.